In recent years, the cost of harvesting trees has increased thereby compelling a search for more economical harvesting methods and apparatus. In the pioneer days, trees were manually harvested one at a time with an axe or saw. This method was satisfactory for pioneer days but as the demand for lumber grew, more productive methods were discovered. Today, there is a variety of logging equipment including tree fellers, debarkers and delimbers which greatly increase productivity. It is desirable to further increase productivity.
To increase productivity tree fellers have been constructed which severe several small trees at one time. While this has the advantage of saving time, it is useful only with small trees which grow very close together.
Normally, larger trees are cut one at a time and individually moved or stacked so that the tree harvester can proceed to the next tree. A certain amount of time is involved in moving or stacking cut trees and during this time the tree harvester is not cutting other trees and is therefore unproductive. Recent tree harvesters have been equipped with accumulators which accumulate cut trees one at a time and hold the trees until it is filled to its capacity of several trees. The trees are then stacked or gang loaded for transport in about the same time it takes to stack or load a single tree. While this is an improvement, there is still a need to be more economical. Apparently, the machines are operated at full human capacity; so, any improvements must relate to the machines themselves.
The state of the art of accumulators for tree harvesters is exemplified by the following U.S. Pat. Nos.:
______________________________________ U.S. Pat. No. Date Inventor ______________________________________ 3,664,391 May 23, 1972 H. D. Coffey 3,805,860 April 23, 1974 L. N. Smith 3,875,983 April 8, 1975 J. Kurelek RE 29,235 May 31, 1977 J. Kurelek 3,886,985 June 3, 1975 A. Larocci et al 3,910,326 Oct. 7, 1975 F. Tucek 3,911,981 Oct. 14, 1975 F. Tucek ______________________________________
U.S. Pat. Nos. 3,875,983, RE 29,235, and 3,886,985 are similar in construction and operation and each utilize two pairs of movable arms. Each arm of each pair of arms is pivotally movable requiring complicated, and therefore expensive, parts and connections to achieve the movement. Similarly, U.S. Pat. No. 3,664,391 uses two pairs of complicated arms with each arm of each pair of arms being pivotally movable. It is therefore desirable to have pairs of arms in which each arm is more simply constructed.
U.S. Pat. No. 3,805,860 uses a single arm for holding the severed trees instead of a pair of arms. Unfortunately, two hydraulic cylinders are required to manipulate the tree accumulating arm so as to remove it from between the accumulated trees and a tree to be accumulated. Obviously, two cylinders double the changes for breakdown or failure and add to the cost and complexity of the accumulator arm as compared with using a single cylinder.
U.S. Pat. No. 3,911,981 uses a single, movable arm for accumulating trees; however, the arm comprises a compound linkage arrangement which, while reducing the number of extra cylinders to zero, is nevertheless a complicated structure. U.S. Pat. No. 3,910,326 has a simpler structure than U.S. Pat. No. 3,911,981. They both have chains, however, which can slip off their sprockets in a logging environment. It is therefore desirable to have a simple accumulator mechanism which can hold and accumulate harvested trees and perform in a logging environment.